A biochemical study of the biological clock of the fungus, Neurospora crassa is proposed. We will employ a particular mutant strain, bd, since it expresses this clock at the morphological level by a rhythmic growth pattern. The rhythm has the characteristics of a circadian one, in that its period is 22 hours, is temperature-compensated, and its phase can be altered by blue light. Previously demonstrated circadian oscillations in neurospora of CO2 output, pyridine nucleotide redox ratio and energy change lead us to propose that the clock mechanisms may be intimately involved with the mitochondria. Our experimental proposals are to elucidate the role of mitochondrial uncoupling in this process. We will employ three separate approaches: 1) Further biochemical studies aimed at gaining a clearer understanding of the nature of the pyridine nucleotide and energy charge oscillations, 2) Physiological studies involving the use of mitochondrial inhibitors as a means of localizing what aspects of its functions are necessary for the expression of the clock, and 3) Genetic studies aimed at determining the effect of various mutations on the expression and periodicity of the clock.